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NLTE analyses of sdB stars: progress and prospects

N. Przybilla·M. F. Nieva·H. Edelmann
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Abstract

We report on preliminary results of a hybrid non-LTE analysis of high-resolution, high-S/N spectra of the helium-rich subdwarf B star Feige49 and the helium-poor sdB HD205805. Non-LTE effects are found to have a notable impact on the stellar parameter and abundance determination. In particular the HeI lines show significant deviations from detailed balance, with the computed equivalent widths strengthened by up to ~35%. Non-LTE abundance corrections for the metals (C, N, O, Mg, S) are of the order ~0.05-0.25 dex on the mean, while corrections of up to ~0.7 dex are derived for individual transitions. The non-LTE approach reduces systematic trends and the statistical uncertainties in the abundance determination. Consequently, non-LTE analyses of a larger sample of objects have the potential to put much tighter constraints on the formation history of the different sdB populations than currently discussed.

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N. Przybilla, M. F. Nieva, H. Edelmann. 2005-12-06. NLTE analyses of sdB stars: progress and prospects. https://arxiv.org/abs/astro-ph/0512151

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